SYNTHESIS, KINETICS, AND PHYSICOCHEMICAL STUDIES OF A NEW MIXED-VALENT HETEROBINUCLEAR CYANO-BRIDGED RUTHENIUM(III)-IRON(II) COMPLEX

The synthesis and physicochemical properties (UV-vis, IR, EPR, cyclic voltammetry) of the complex K5[Ru(III)-(edta)(NC)Fe(II)(CN)5] (2) are described. Complex 2 shows an intervalence absorption maximum (E(op)) at 940 nm in H2O (at room temperature), and the position of the absorption maximum shifts with change in temperature (20-60-degrees-C). The kinetics of the formation of complex 2 was studied spectrometrically by stopped-flow technique. The rate of formation of complex 2 was found to be first-order with respect to both Ru(edta)(H2O)- and Fe(CN)64-concentrations and highly dependent on the ionic strength of the reaction medium. Rate and activation parameters (DELTAH(double dagger) and DELTAS(double dagger)) calculated for this reaction are inconsistent with the proposed associative mechanism. The intervalence thermochromism for this ground-state mixed-valence complex 2 is discussed with reference to the data reported for the similar [Ru(III)(NH3)5(NC)Fe(II)(CN)5]- complex.